The present invention relates to a bulletproof glass screen which is used for applications requiring protectiveness and transparency and a bulletproof glass screen device based on such a bulletproof glass screen.
A conventional bulletproof glass generally consists of a laminate of heat-treated, annealed glass plates whose thickness is from 10 to 12 mm. This kind of bulletproof glass as a laminate of, for example, four glass plates has an overall thickness of 40 to 50 mm. A laminate like this requires a high production cost and is poor in machinability and also weighty, which leads to poor workability. There are bulletproof screens which use polycarbonate resin plates instead of glass plates. However, this type of bulletproof screen requires a very high production cost and the surface may become yellowish for aged deterioration. In addition, since it takes the form of a plate, the yellowish surface or other part as a phenomenon of deterioration with time tends to be conspicuous.
An example of conventional bulletproof glass is the published Japanese translation of PCT international publication for patent applications No. 506056/1991. This bulletproof glass screen device is structured of a plurality of glass plates. Each surface of glass plates is covered by fracture-proof safety film. The glass plates are spaced at regular intervals. However, when this structure is used, the device must be wide and relatively heavy, resulting in a deterioration in workability.
The present invention has been made in view of the above circumstances and provides a bulletproof glass screen and a bulletproof glass screen device which are relatively lightweight and workable and provide a relatively high protectiveness and transparency.
In order to achieve the above-described object, a structure of the present invention is explained by reference to drawings illustrating embodiments of the invention. Each of these bulletproof glass screens 1 (1-1 to 1-7) is characterized in that at least one of the front and rear faces of a laminated glass 2 is covered by at least one sheet of plastic fracture-proof film 3. The fracture-proof film 3 can be attached only to at least one of the front and rear faces of the bulletproof glass screen 1. It is desirable to attach the fracture-proof film 3 to the rear side of the bulletproof glass screen 1, or the opposite of its impact surface. There are cases in which the condition of the surroundings including the inside or outside of a building or room is known and which direction bullets are most likely to come from is obvious. Usually it is thought that bullets are more likely to come from the outside of a building than from the inside or more likely to come from the outside of a room than from the inside. Therefore, in such cases, it is effective that the bulletproof glass screen""s inside surface which is inside the building or room is covered by fracture-proof film. However, if the building is used as a shooting gallery or the like, it is more likely that bullets come from the inside of the building; thus in this case it is effective that the bulletproof glass screen""s outside surface which is outside the building or room is covered by fracture-proof film.
The fracture-proof film 3 can be attached to both the front and rear faces of the bulletproof glass screen 1. If the fracture-proof film 3 is attached to both the front and rear faces of the screen, it is useful for a situation in which bullets may impact against both the front and rear faces of the bulletproof glass screen 1. When it is predictable that under some condition (during a certain period or time zone, etc.) bullets fly from a specific direction (for example, if shooting galleries are located on both sides of the screen and are alternately used for firing in the morning and afternoon for the reason of time-consuming preparation of the shooting galleries or other reason), covering of both the front and rear faces of the bulletproof glass screen 1 by the fracture-proof film 3 is effective. Also there is another situation in which, although bullets usually fly from a fixed direction, bullets can fly from the opposite direction in some special occasions. Covering of both the front and rear faces of the bulletproof glass screen 1 by the fracture-proof film 3 is also effective that not only the case where bulletproofing is primarily intended as a countermeasure against shooting from the outside of the building, but also the case where it is required to prevent bullets or splinters of a bullet from hitting a passer-by outside the building due to shooting or an explosion inside it.
Further, in the case of a bulletproof glass screen device as mentioned later, if the bulletproof glass screen 1 is assembled in the field where the device is installed, covering of both the front and rear faces of the bulletproof glass screen 1 by the fracture-proof film 3 is effective because there is a possibility of assembling the screen the wrong way.
The fracture-proof film 3 is generally made to adhere to all or virtually all the above-said surface of the bulletproof glass screen 1. All or virtually all the above-said surface refers to all or virtually all the surface of the screen except the rim for fitting the bulletproof glass screen 1, for example, into a window frame. If, for fitting into the window frame or in connection with any other thing pertaining to the building, some part of the surface of the bulletproof glass screen 1 is substantially exposed to the outside, it is a good idea to cover it by the fracture-proof film 3. It is also possible to attach the fracture-proof film 3 to 20 part of the above-said surface of the bulletproof glass screen 1. This means that the fracture-proof film 3 may be attached to the part of the bulletproof glass screen 1 which bullets may hit. If part of the bulletproof glass screen surface exposed to the outside is covered by the fracture-proof film 3, a bulletproof material as mentioned later like a metal net or metal board may be provided facing the surface of the bulletproof glass screen 1 which is not covered by the fracture-proof film 3.
The above-mentioned fracture-proof film 3 is plastic film: it may be, for example, polyethylene resin, polyester resin, vinyl chloride resin or polycarbonate resin film.
At least one sheet of above-said fracture-proof film 3 is used; however, the number of sheets used may be as desired or varied depending on the structure of the laminated glass 2 of the bulletproof glass screen 1 or the environment or situation in which it is installed. As the environment or situation in which the laminated glass 2 is installed changes, the number of sheets of fracture-proof film 3 may be increased or decreased later. Furthermore, the fracture-proof film 3 may be later attached to the already installed laminated glass 2 with no fracture-proof film 3 in order to make up a bulletproof glass screen 1 according to the present invention. When more than one sheet of fracture-proof film are attached to the laminated glass 2, the fracture-proof film sheets may be of the same type or of different types.
One sheet of fracture-proof film 3 may comprise a single layer of film. Alternatively, it may be a multi-layered film in which a plurality of single film layers of the same plastic material are laminated, or a multi-layered film in which a plurality of single film layers of different plastic materials are laminated. It is desirable that one sheet of fracture-proof film 3 is a multi-layered film for the sake of increased strength and comprises layers of the same plastic material for manufacturing ease. For instance, it is recommended that it be a multi-layered film as a laminate of plural polyethylene plastic film layers.
In manufacturing a sheet of multi-layered fracture-proof film 3, a plurality of single layer plastic films are laminated, pressed and bonded to each other in a way that their drawing or pulling directions, or molecular elongation or fiber directions cross at right angles or at approximately right angles to each other.
It is desirable that the thickness of a sheet of fracture-proof film 3 is not less than 150 xcexcm, more desirably 350 xcexcm or more. The thickness of a sheet of fracture-proof film 3 may be equal to only the thickness of the film itself. Also, if there is an adhesive layer which has been made by coating or spraying an adhesive agent on the surface of the fracture-proof film for bonding to plate glass or another sheet of fracture-proof film (in the case of using plural sheets of fracture-proof film), the thickness of a sheet of fracture-proof film 3 may be equal to the sum of the thickness of the film sheet and that of the adhesive layer.
The fracture-proof film 3 is intended to be attached to plate glass which is component of a laminated glass in order to prevent fracturing of the plate glass, scattering of splinters of glass or the like. On the bonding surface of the fracture-proof film 3, an adhesive layer may be previously made by coating or spraying an adhesive agent such as a water-activated pressure-sensitive adhesive agent for bonding the fracture-proof film 3 to plate glass or another fracture-proof film sheet (in the case of using plural sheets of fracture-proof film), before bonding it to the plate glass.
This makes it possible to join a fracture-proof film sheet to glass plate or two fracture-proof film sheets together as follows: before starting bonding as mentioned above, water is coated, sprayed or otherwise applied to the bonding surface of the fracture-proof film or plate glass; then the bonding surfaces of the film and glass plate or those of one film sheet and another one are made to contact and overlap each other; finally pressure is applied to the adhesive layer to bond them together.
The above-said laminated glass 2 is composed of plural glass plates 4 bonded through a layer or layers of intermediate membrane 5. The number of glass plates 4 which constitute the laminated glass 2 may be 2, 3, 4 or more. However, for the purpose of ensuring lightness or handling ease as a bulletproof glass screen, it is desirable to use two, three or four glass plates (layers) or so; further, three glass plates are more desirable than two and four more desirable than three. The thickness of each of the plural glass plates which constitute the laminated glass 2 is between about 3 mm and about 19 mm. The laminated glass 2 may be composed of plural glass plates of the same type or plural glass plates of different types.
Regarding the structure of the above-said intermediate membrane layer 5, it is possible to use a single intermediate membrane or plural ones, or combine it or them with an adhesive layer or adhesive layers of adhesive agent or the like. When the laminated glass is produced by inserting an intermediate membrane layer between plural glass plates, if the intermediate membrane layer 5 comprises one or more intermediate membranes, they may be bonded together by applying pressure to the intermediate membrane layer through the glass plates (pressure bonding) or heating the intermediate membrane layer through the glass plates (thermal bonding) or by a combination of the pressure and thermal bonding methods. Also, if the intermediate membrane layer 5 is composed of one or more intermediate membranes and an adhesive layer(s), they may be bonded together by using the adhesive layer(s) on the intermediate membrane layer (adhesive bonding), applying pressure to the intermediate membrane layer through the glass plates (pressure bonding) or heating the intermediate membrane layer through the glass plates (thermal bonding) or by a combination of these adhesive, pressure and thermal bonding methods. It is preferable that the intermediate membrane which constitutes an intermediate membrane layer 5 is a plastic film membrane or the like; typically a film membrane made of PVB, polyethylene, EVA or similar plastic material is used. Preferably the thickness of each intermediate membrane layer should be 15 mils (approx. 0.38 mm) or more. When one intermediate membrane layer is to be composed of more than one intermediate membrane, it may be produced by using two, three or more plastic film sheets of the same type, or two, three or more plastic film sheets of different types.
The number of intermediate membrane layers 5 should be subtracted 1 from the number of laminated glass plates; one intermediate membrane layer is sandwiched between two neighboring glass plates as components of a laminated glass.
The each glass plate 4 which constitute the above-said laminated glass 2 may be all equal in thickness. However, with a view to increasing protectiveness, it is desirable that the front glass plate 4, or the glass plate on the impact side (that is, the side not covered by fracture-proof film when only one side of the bulletproof glass screen is covered by such film), is thicker than the rear glass plate 4 behind it.
In a bulletproof glass screen 1 as mentioned above according to the present invention, even if the glass is broken by a bullet, the polyethylene resin fracture-proof film 3 and the intermediate membrane layer 5 are effective in preventing scattering of glass splinters and rather holding them, so the kinetic energy of the bullet is absorbed and the velocity of the bullet goes down. This makes it possible to use the glass which is thinner and lighter than a conventional bulletproof glass.
In each of the above-said bulletproof glass screens 1, its rim is fixed into the groove of a frame 7 through joint sealant such as beads or battens. The bulletproof glass screen 1 may be fixed in its vertical, horizontal or oblique position with joint sealant in the groove of the frame 7. Also, in front of the bulletproof glass screen 1, a see-through metal net 6 may be located away from the screen by a specified distance.
When a bulletproof glass screen device has a structure like this, the energy of a bullet is first absorbed by the metal net 6 and the bullet reaches the above-said bulletproof glass screen 1 according to the present invention.
It is preferable that the glass plates and fracture-proof film used in the present invention are transparent or translucent from the viewpoint of visibility and natural illumination; however, basically they may be of any other type. They may be either colorless or colored. In the above-said laminated glass, the surface on which the fracture-proof film is laid may be flat or curved or bent. It is desirable that the laminated glass has a smooth surface, but the one whose surface is not smooth is also acceptable.
A bulletproof glass screen or bulletproof glass screen device according to the present invention can be used for purposes other than bulletproofing such as protection from relatively small flying objects or collapsing objects.
In a bulletproof glass screen and a bulletproof glass screen device as mentioned above according to the present invention, even if the glass is broken by a bullet, the fracture-proof film and the intermediate membrane layer of the laminated glass are effective in preventing scattering of glass splinters and rather holding them, so the kinetic energy of the bullet is absorbed, resulting in a decrease in the velocity of the bullet and an increase in protectiveness. This makes it possible to use the bulletproof glass which is thinner and lighter than a conventional bulletproof glass; thus it can be produced easily and its workability is high.